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Appendix C
AT Commands

 

AT Commands

This Appendix details the "AT" commands used by modems and ISDN TAs. This information is provided to assist users who are using the serial port of LevelOne WBR-1100TX.

It is not relevant to Cable or DSL modems connected to the WAN (Ethernet) port.

Required Settings

For the LevelOne Wireless Broadband Router to use the Serial Port correctly, the modem or ISDN TA must be set as follows.

Setting

AT Command

Fixed baud rate setting
AT&B1
RTS/CTS flow control
AT&K3
DCD to track the presence of a carrier
AT&C1
DTR off to hang-up modem
AT&D2
DSR always on
AT&S0

If your Modem or ISDN TA uses the commands above, then the Initial String would be as follows:

        AT&F&B1&K3&C1&D2&S0X4

Notes:

Finding the current Initial String

If your modem or ISDN TA is already working correctly using the PC's serial port, but you don’t know what the initialization string is, you can use the following procedure to find out.

  1. Select My Computer, then Dial-Up Networking.
  2. Select the icon for your connection, then Properties.
  3. Click the Configure button, then the Connection tab, as shown below.

    Figure 50: Connection Properties (W95/98)

  4. Select Advanced to see the screen below.

    Figure 51: Advanced Connection (W95/98)

  5. Check the option Record a log file. Then click OK and exit.
  6. Use Dial-up Networking to make your on-line connection normally. A log file MODEMLOG.TXT will be created in your Windows directory.
  7. Use Notepad or another editor to read and print the file MODEMLOG.TXT.
  8. Examine the file to determine the Initial String value. It will be near the beginning of the file, and look something like the example shown previously.

 

Standard AT Commands

Most modems use the standard AT commands, as shown in the following tables. Consult the manual for your modem to set what AT commands it supports.

Note that the trailing "n" in many commands indicates a number.
The allowable numbers, and their effect, are listed below the command.

Command

Description

<any key>
Terminate current connection attempt
+++
Escape sequence code, entered in data state, wait for modem to return to command state
ATA
Force answer mode on-line
ATBn
Handshake operation

B0
Select ITU-T V.22 for 1200 bps communication

B1
Select Bell 212A for 1200 bps communication
ATD
Dial number and options that follow

P
Pulse dial

T
Tone dial

,
Pause for a specified time

;
Return to command state after dialing

!
Hook flash, call transfer

W
Wait for second dial tone

@
Wait for 5-second silence before proceeding, otherwise return O ANSWER"

R
Reverse Dial (Originate a call in answer mode)
ATDL
Dial last number
ATDSn
Dial number stored in NVRAM at position n. (n=0..9)
ATEn
Command mode local echo of keyboard commands

E0
Echo off

E1
Echo on
ATHn
On/Off hook control

H
Hang up modem

H0
Hang up (on hook), same as ATH

H1
Get off hook
ATIn
Display inquired information

I0
Display product code

I1
Display product information and ROM checksum

I2
Link status report
ATLn
Speaker volume control. n=0-7
ATMn
Speaker control

M0
Speaker always off

M1
Speaker on until carrier is detected

M2
Speaker always on

M3
Speaker on after last digit dialed, off at carrier detect
ATNn
Ring volume control, n=0 disables ring function. (n=0..7)
ATO
Return to on-line state
ATP
Pulse dial
ATQn
Result code displayed

Q0
Modem returns result code

Q1
Modem does not return result code

Q2
Return result code but quiet in answer mode (will not show in AT&Vn)
ATS0=n
Number of rings required before modem answers. n=0 disables auto-answer.
ATSr.b=n
Set bit b of S-register r to n. (n=0 or 1)
ATSr.b?
Inquiry bit b of S-register r
ATSr=n
Set S-register r to value n, where n is a decimal number between 0-255
ATSr?
Display value stored in S-register r
ATT
Tone dial
ATVn
Verbal/Numeric result codes

V0
Display result codes in numeric form

V1
Display result codes in verbose form
ATXn
Result code options. (n=0..7)
ATZn
Reset the modem and set power-on profile. (n=0..4)

Zn
Reset modem and load user profile n (n=0..3)

Z4
Reset modem and load factory settings
AT$
Help, Basic command summary
AT&$
Help, Extended AT& command summary
AT*$
Help, Extended AT* command summary

 

Extended "AT&" Commands

(Includes RTS/CTS Flow Control Commands)

Command

Description

&Bn
Data rate, terminal-to-modem

&B1
DTE/DCE rate fixed at DTE setting
&Cn
Carrier Detect operations

&C1
Carrier Detect tracks presence of carrier
&Dn
Data Terminal Ready (DTR) operations

&D2
DTR off causes modem to hang up
&F
Load the default factory settings,
&Kn
Data flow control, DTE/DCE, n=0,3,4

&K0
Flow control disabled

&K3
Hardware (RTS/CTS) flow control

&K4
Software (XON/XOFF) flow control
&Sn
Data Set Ready (DSR)

&S0
DSR overridden, DSR always on

 



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